Fluidic adaptive lens

ABSTRACT

A fluidic adaptive lens, a multi-lens apparatus employing the fluidic adaptive lens, and a method of fabricating a fluidic adaptive lens are disclosed. The lens includes a first partition that is flexible and optically transparent, and a second partition that is coupled to the first partition, where at least a portion of the second partition is optically transparent, and where a first cavity is formed in between the first partition and the second partition. The lens further includes a first fluidic medium positioned within the cavity, the fluidic medium also being optically transparent; and a first device capable of controlling a parameter of the fluidic medium, where when the parameter of the fluidic medium changes, the first partition flexes and an optical property of the lens is varied.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. provisional patentapplication No. 60/558,293 entitled “Fluidic Adaptive Lens” filed onMar. 31, 2004, which is hereby incorporated by reference herein.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

This invention was made with United States Government support awarded bythe following agencies: Defense Advanced Research Projects Agency(DARPA) Grant No. F49620-02-1-0426; and Air Force Office of ScientificResearch (AFOSR) Grant No. F49620-02-1-0426. The United StatesGovernment has certain rights in this invention.

FIELD OF THE INVENTION

The present invention relates to optical lenses and more particularlyrelates to vision correction lenses and zoom lenses such as are employedin various optical systems.

BACKGROUND OF THE INVENTION

Optical lenses are employed in a variety of devices for many purposessuch as modifying focus and magnification. Many conventional devicesthat employ optical lenses use lenses that are made from solidmaterials, such that the optical properties of the lenses (e.g., theirfocal distances) remain constant or nearly constant over time. Forexample, eyeglasses used for vision correction typically are made ofsolid materials such as glass and plastic. Similarly, cameras and otheroptical systems such as microscopes, video monitors, video recorders,copy machines, scanners, etc. commonly employ solid lenses.

Although lenses made from solid materials are generally robust andmaintain their optical properties over time, the use of such lenses alsohas numerous disadvantages. With respect to vision correction lenses,for example, the power of vision correction is fixed at the time offabrication of the lenses. As a consequence, today's eyeglass lensesoften cannot be mass produced at low cost because the lenses arespecially fabricated for each and every patient. Since each patient hashis/her unique power requirement for eye correction, the patient has tosee an ophthalmologist or optometrist to measure his/her eye correctionpower first before having the vision correction lenses fabricated. Inaddition, machining glass or plastic material to the precise shape of alens according to a prescription is, by itself, a relatively high-costand low throughput process. Often, it takes several days or even weeksfor patients to receive a new pair of eyeglasses. In comparison withcertain off-the-shelf vision products such as sunglasses,vision-correcting eyeglasses designed and fabricated using currenttechnology are particularly expensive and complicated to manufacture.

Further, vision correction lenses used in today's eyeglasses do not havethe flexibility to handle various situations with which wearers areoften confronted. For example, the optimal eye correction for a givenindividual frequently varies depending upon a variety of factors, suchas the person's age, the person's lifestyle, and various practicalcircumstances. Consequently, an adult typically needs to replace his orher eye correction lenses every few years. For juveniles or adolescents,updating of vision correction eyeglasses often is required morefrequently than for adults.

For certain persons, particularly persons in their 50s and over, thevision correction that is needed for viewing near objects can be verydifferent from the vision correction that is needed for viewing distantobjects. To provide different levels of vision correction via a singlepair of eyeglasses, many of today's eyeglasses employ bifocal lenses (oreven tri-focal or otherwise multi-focal lenses), in which differentsections of a given lens provide different optical properties. Yet suchbifocal lenses offer at best an inconvenient solution to the problem ofhow to provide varying levels of vision correction on a single pair ofeyeglasses. Traditionally, bifocal lenses are formed from pairs of lensportions that are positioned or fused adjacent to one another along amidline of the overall lens. Because the midline between the lensportions is a perceptible boundary between the lens portions, suchlenses are often cosmetically undesirable.

Although newer bifocal lenses are available that are not as cosmeticallyundesirable, insofar as the lenses are graded such that there is only agradual change of correction power from region to region on the lens andsuch that a clear boundary separating different regions of the lens doesnot exist, such newer bifocal lenses nevertheless share other problemswith traditional bifocal lenses. In particular, because differentportions of the lenses have different vision correction characteristics,the wearer's field-of-view at any given time or circumstance via thelenses is still compromised insofar as only certain portions of thelenses provide the appropriate optical characteristics for the wearer atthat time/circumstance.

Additionally, while many persons do not require bifocal lenses, thesepersons can nevertheless prefer that their eyeglasses provide differentamounts of vision correction in different situations. For example, thepreferred amount of vision correction for a person when driving a car orwatching a movie can differ from the preferred amount of visioncorrection for that person when reading a book or working in front of acomputer screen.

For at least these reasons, therefore, it is apparent that the use ofsolid lenses with fixed optical properties in eyeglasses isdisadvantageous in a variety of respects. Yet the disadvantagesassociated with using solid lenses with fixed optical properties are notlimited to the disadvantages associated with using such lenses ineyeglasses/eyewear. Indeed, the use of solid lenses with fixedproperties in a variety of devices such as cameras, microscopes, videomonitors, video recorders, copy machines, scanners, etc. also presentssimilar disadvantages.

Further, the use of solid lenses with fixed optical properties entailsadditional disadvantages in systems that employ combinations of lensesthat interact with one another to provide overall optical properties.Such systems include, for example, zoom lens systems in which two ormore optical lenses of fixed optical properties are moved relative toone another to change optical properties of the overall combination oflenses forming the zoom lens. Because the optical properties of theindividual lenses used in such systems are fixed, the overall opticalproperties of the combinations of lenses depend upon other factors,particularly the relative positioning of the individual lenses.Consequently, to provide the desirable features and capabilitiesassociated with systems such as zoom lens systems, complicated andexpensive mechanical and/or other components and techniques must beemployed to achieve the desired effects.

In particular with respect to zoom lens systems, conventional systemswith zooming capabilities are typically more expensive and often morebulky/heavy than systems without such capabilities. The most importantfigure of merit for zoom lenses is the zoom ratio. The higher the zoomratio is, the more costly the system becomes. A typical camera has anoptical zoom ratio of about 3, and some high-end imaging systems have azoom ratio of greater than 10. Currently, all optical zoom lensesachieve zoom-in and zoom-out functions by changing the distance(s)between the individual lenses forming the overall zoom lens. Thisinvolves high-precision mechanical motions of the lenses over a typicalrange of several centimeters. To provide highly-precise, reliablerelative movement of the lenses typically requires a mechanical systemthat is complicated, slow, bulky and expensive.

The need to vary lens distance to achieve zooming has become a roadblockfor incorporating zooming features into many new and emergingapplications. Many modern “electronic gadgets” including cell phones,personal digital assistants (PDAs), and notebook computers are equippedwith CCD or CMOS cameras. Implementation of cameras into such gadgetshas evolved from being a novelty to being a standard feature, and manysuch gadgets now support imaging-related functions that involve not justimaging but also recording, videophone capabilities, and videoconferencing. Yet conventional zoom lenses are difficult to incorporateinto these small electronic gadgets and their optical devices.

Therefore, it would be advantageous if one or more new types of lensesand/or lens systems could be developed that alleviated the disadvantagesassociated with using solid lenses having fixed optical properties asdiscussed above. In particular, it would be advantageous if a new typeof lens or lens system could be developed for implementation ineyeglasses that made it possible to easily and inexpensively adjustoptical characteristics of the eyeglasses without entirely replacing thelenses. It would further be advantageous if the optical characteristicsof the lenses could be flexibly varied over a wide spectrum, rather thansimply to a limited number of discrete levels. It additionally would beadvantageous if variations in the optical properties of a lens could beapplied to the entire lens, so that, for example, variations in theoptical properties of the lens would apply to an entire range of visionof a wearer of eyeglasses employing the lens, rather than merely aportion of that range of vision.

It further would be advantageous if the new type of lens or lens systemcould also or alternatively be implemented in other systems that employlenses such as cameras, microscopes, video monitors, video recorders,optical recording mechanisms, surveillance equipment, inspectionequipment, agile imaging equipment, target tracking equipment, copymachines, scanners, etc. It additionally would be advantageous if thenew type of lens or lens system could be implemented in zoom lenssystems in a manner that reduced the need for complicated mechanicalsystems for controlling relative positioning of multiple lenses withinthe zoom lens systems. It also would be advantageous if a zoom lenssystem employing the new type of lens or lens system could be compactlyimplemented on one or more types of physically small “electronicgadgets” such as cell phones, personal digital assistants (PDAs), ornotebook computers.

BRIEF SUMMARY OF THE INVENTION

The present inventors have recognized that many of the above-mentioneddisadvantages associated with conventional eyeglasses and opticalsystems, including systems employing multiple lenses such as zoom lenssystems, can be alleviated or eliminated if the eyeglasses or opticalsystems employ lenses that are variable or adaptive in terms of theiroptical properties. The present inventors further have discovered thatlenses having adaptive optical properties can be formed through the useof one or more optically transparent flexible diaphragms/membranes thatrespectively separate pairs of fluidic media. By appropriately varyingone or more of the pressures of the fluidic media, which results inchanges in the positioning of the membranes and the amounts of one ormore of the respective fluidic media through which light passes, theoptical properties of the lenses can be varied.

In particular, the present invention relates to a lens device thatincludes a first partition that is flexible and optically transparentand a second partition that is coupled to the first partition, where atleast a portion of the second partition is optically transparent, andwhere a first cavity is formed in between the first partition and thesecond partition. The lens device further includes a first fluidicmedium positioned within the cavity, the fluidic medium also beingoptically transparent, and a first component capable of controlling aparameter of the fluidic medium. When the parameter of the fluidicmedium changes, the first partition flexes and an optical property ofthe lens is varied.

The present invention additionally relates to a multi-lens apparatuscomprising a first fluidic adaptive lens, a second fluidic adaptivelens, and an intermediate structure coupling the first and secondfluidic adaptive lenses, where the intermediate structure is at leastpartly optically transparent.

The present invention further relates to a method of fabricating afluidic adaptive lens device. The method includes providing a firststructure having a first cavity, where the first cavity is onlypartially enclosed by the first structure, and attaching a firstflexible layer and the first structure to one another in a manner thatsubstantially encloses the first cavity. The first cavity is capable ofbeing filled with a first fluid so that the first structure, firstflexible layer, and first fluid interact to form the fluidic adaptivelens device.

The present invention further relates to a method of operating a lensdevice. The method includes providing a lens structure including aflexible layer and a rigid structure coupled to one another and forminga cavity, and adjusting a fluid pressure of fluid within the cavity soas to adjust a flexure of the flexible layer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a pair of eyeglasses within which fluidic adaptive lensesare employed;

FIGS. 2 a and 2 b show, in simplified schematic form, cross-sectionalviews of a convex fluidic adaptive lens and a concave fluidic adaptivelens, respectively;

FIGS. 3 a and 3 b show, in more detail, cross-sectional views of theexemplary convex and concave fluidic adaptive lenses of FIGS. 2 a and 2b, respectively, along with related support structures;

FIGS. 4 a and 4 b show two cross-sectional views of other exemplaryembodiments of fluidic adaptive lenses that maintain a constant outershape;

FIG. 5 shows, in simplified schematic form, a hydraulic circuit that canbe employed with respect to lenses such as those in FIGS. 2 a and 2 b;

FIG. 6 is a simplified flow chart showing exemplary steps of a procedurefor creating a hydraulic circuit such as that of FIG. 5 employing lensessuch as those in FIGS. 3 a-3 b;

FIG. 7 shows in schematic form a zoom lens system employing at least onefluidic adaptive lens;

FIG. 8 shows a cross-sectional view of an exemplary fluidic adaptivelens capable of being used to achieve a wide focal-distance tuningrange;

FIG. 9 is a graph showing how a focal length of the fluidic adaptivelens of FIG. 8 varies with fluidic pressure in one embodiment;

FIGS. 10 a-10 d show in schematic form steps of an exemplary process forconstructing a lens structure utilizing fluidic adaptive lenses that canbe employed in a zoom lens system;

FIGS. 11, 12 a and 12 b show three cross-sectional views of otherexemplary embodiments of lens structures;

FIGS. 13 a-13 b, 14 a-14 c and 15 a-15 d show cross-sectional views ofexemplary embodiments of two-lens structures formed from variouscombinations of the lens structures shown in FIGS. 11, 12 a and 12 b;

FIG. 16 is a graph showing the variation of magnification provided by anexemplary zoom lens system, in accordance with one of the embodiments ofFIGS. 13-15, as a function of front lens power; and

FIG. 17 is a simplified flow chart showing exemplary steps of aprocedure for creating a two-lens structure such as those shown in FIGS.13 a-13 b.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention relates to the design and construction of fluidicadaptive lenses, as well as the use of one or more such lenses in avariety of environments such as in eyeglasses and zoom lens systems.FIGS. 1-6 generally relate to the design and implementation of fluidicadaptive lenses for use in eyeglasses that are capable of providingdynamically-adjustable vision correction power. FIGS. 7-17 generallyrelate to the design and implementation of fluid adaptive lenses andcombinations of such lenses for use in zoom lens systems that can beincorporated into a variety of devices such as, for example, cameras incellular phones, and that are capable of providing variable zoomingcapability without the need for complicated mechanical devices forphysically moving multiple lenses toward or away from one another.

Although FIGS. 1-17 particularly relate to the design and implementationof fluidic adaptive lenses for use in eyeglasses and zoom lens systems,the present invention is also intended to encompass the use of these orsimilar fluidic adaptive lenses in a variety of other applications andcircumstances including, for example, a wide variety of other electronicand other devices such as microscopes, video monitors, video recorders,optical recording mechanisms, bar-code readers, systems with macro (ormagnifying) functions, surveillance equipment, inspection equipment,agile imaging equipment, target tracking equipment, copy machines,scanners, cell phones, personal digital assistants (PDAs), notebookcomputers, telescopes, magnifying glasses, optometrist testingequipment, and other devices that require lenses. Indeed, the presentinvention relates simply to the design and implementation of fluidicadaptive lenses generally, independent of any particular application ofsuch lenses. The present invention is intended to encompass a variety ofdifferent lenses, lens structures and lens systems that employ one ormore fluidic adaptive lenses that are variable in terms of opticalcharacteristics, including a variety of lens types such as convex,concave, convex-concave, positive or negative meniscus, plano-convex,plano-concave, biconvex and biconcave lenses.

Referring to FIGS. 1, 2 a and 2 b, exemplary fluidic adaptive lensescapable of being implemented in eyeglasses are shown in schematic form.FIG. 1 shows an exemplary pair of eyeglasses 5 in which two fluidicadaptive lenses 6,7 are supported by frames 8. Turning to FIGS. 2 a and2 b, those figures show in cross-section two different types of lensesthat could be implemented as the lenses 6, 7 in the eyeglasses 5 ofFIG. 1. FIG. 2 a shows in general form a first fluidic lens 1 that canbe used to correct hyperopia (farsightedness). As shown, the fluidiclens 1 is a convex adaptive vision correction lens that contains a firstmedium 20 that is a higher index fluid, a second medium 10 that is alower index fluid, and a flexible membrane (or diaphragm) 30 thatseparates the two media. The flexible membrane 30 bends toward the lowerindex side when the pressure of the higher index fluid is greater thanthat of the lower index fluid. In contrast to FIG. 2 a, FIG. 2 b showsthe general situation of a second fluidic lens 2 that can be used tocorrect myopia (nearsightedness). As shown, the fluidic lens 2 is aconcave adaptive vision correction lens that contains a first medium 22that is a higher index fluid, a second medium 12 that is a lower indexfluid, and a flexible membrane (or diaphragm) 32 that separates the twomedia. The membrane 32 bends towards the higher index side when thepressure of the lower index fluid is greater than that of the higherindex fluid.

The respective flexible membranes 30, 32 are deformed by the pressuredifferences between the respective pairs of media 10, 20 and 12, 22. Forexample, if the pressure on the higher index medium side is greater thanthat of the lower index medium side, the membrane will bend towards thelow index medium, as shown in FIG. 2 a, to form an effective convex lenscapable of correcting the hyperopia (farsightedness) problem. On theother hand, if a higher fluidic pressure exists on the low-index mediumside, the membrane will bend towards the high-index medium to form aneffective concave lens capable of correcting the myopia(nearsightedness) problem (see FIG. 2 b).

Turning to FIGS. 3 a and 3 b, exemplary fluidic lenses 36 and 46 areshown in cross-section, respectively. The lenses 36, 46 show in greaterdetail exemplary structures that can be employed as the convex andconcave adaptive vision correction lenses 1, 2 shown schematically inFIGS. 2 a and 2 b, respectively. As shown, the lenses 36 and 46 eachinclude a segment of transparent rigid material 31 and 41, respectively,a first fluidic medium 32 and 42, respectively, a second fluidic medium33 and 43, respectively, and a flexible membrane (or diaphragm) 34 and44, respectively. In the present embodiment, the second fluidic media33,43 are shown as air outside of the lenses 36,46, although thosefluidic media could be other fluids (gaseous or liquid) as well.

Additionally, each of the lenses 36, 46 includes a respective wall 37,47 that supports its respective membrane 34, 44 with respect to itsrespective transparent rigid material 31, 41. The walls 37, 47 encircletheir respective lenses 36, 46, which typically are circular oroval-shaped when viewed from the front of the lenses (albeit the lensescould have other shapes as well). The walls 37, 47 and transparent rigidmaterials 31, 41 respectively form fluidic lens chambers. The fluidiclens chambers (e.g., comprising walls 37, 47 and transparent rigidmaterials 31, 41), along with the membranes 34, 44, define respectiveinternal cavities 38,48 within which are the first fluidic media 32, 42.The walls 37, 47 of the fluidic lens chamber define respective channels39,49 by which the first fluidic media 32, 42 can enter and exit thecavities 38, 48. In certain embodiments, the walls 37, 47 can be formedwithin the frames 8 of the eyeglasses 5. Also as shown in FIGS. 3 a and3 b, arrows 35, 45 respectively represent the directions of the flow(and/or pressure) of the media 32, 42 with respect to the cavities 38,48 that are appropriate for causing the respective lenses 36, 46 tobecome convex and concave, respectively. As shown, the first fluidicmedium 32 tends to flow into the cavity 38 causing the membrane 34 toexpand outward while the first fluidic medium 42 tends to flow out ofthe cavity 48 tending to cause the membrane 44 to contract inward.

By controlling the amounts of the first fluidic media 32, 42 that flowin and out of the cavities 38, 48 (which can depend upon the pressure ofthose media), the optical properties of the lenses 36, 46 can be varied.In particular, because in the present embodiment the second fluidicmedia 33, 43 are the air of the atmosphere, by applying a positivepressure to the first fluidic medium 32 (e.g., a pressure greater thanthe atmospheric pressure), the membrane 34 tends to expand outward asshown in FIG. 3 a, and by applying a negative pressure to the firstfluidic medium 42 (e.g., a pressure less than the atmospheric pressure),the membrane 44 tends to contract inward as shown in FIG. 3 b. Thus, thelenses 36 and 46 could in fact be the same lens, which in one state hasbeen configured as a convex lens and in another state has beenconfigured as a concave lens.

Although the lenses 36, 46 shown in FIGS. 3 a and 3 b are physicallycapable of operating as lenses (e.g., capable of causing light to befocused or to be dispersed), the structures of these lenses are notpreferred. Because the membranes 34, 44 in these embodiments are exposedto the outside atmosphere and outside environment, atmospheric pressurechanges, temperature changes and/or external impacts all can damage orchange the optical properties of the lenses 36, 46, such that the lensescan suffer from reliability, stability (including drift of the lenses'optical properties), and performance issues. Particularly in the mode ofthe concave lens 46 of FIG. 3 b, the fluidic chamber has to maintain anegative pressure relative to the atmosphere, which requires anair-tight design that is harder to achieve and keep stable than aleak-tight design for positive fluid pressure. Consequently, whilesuitable for some applications, the lenses 36, 46 can be used ineyeglasses primarily only when high viscosity and very low vaporpressure fluid is used as the liquid medium, which limits themanufacturability of the devices.

Two improved designs for fluidic adaptive lenses that are capable ofbeing employed as the lenses 6 and 7 of the eyeglasses 5, and that aremore robust and stable in operation than the lenses 36, 46 of FIGS. 3a-3 b, are shown in FIGS. 4 a and 4 b as lenses 50 and 60, respectively.To minimize the influence of the environment such as atmosphericpressure, the lenses 50, 60 employ rigid materials to form all (ornearly all) of the outer surfaces of the lenses. As shown, the lens 50of FIG. 4 a in particular includes two fluid chambers, while the lens 60of FIG. 4 b includes three fluidic chambers.

Referring to FIG. 4 a, the lens 50 includes several components. First,the lens 50 includes a pair of transparent, rigid outer surfaces 51 (onboth sides of the lens) that are capable of keeping the outer shape ofthe lens unchanged as in the case of conventional solid lenses.Additionally, the lens 50 includes a flexible membrane (or diaphragm) 54positioned in between the rigid outer surfaces 51, and a pair of walls57 that support the membrane 54 in relation to the surfaces 51. Further,a lower index first fluidic medium 52 is contained within a first cavity58 defined by the membrane 54, one of the walls 57 and one of the rigidouter surfaces 51, and a higher index second fluidic medium 53 containedwithin a second cavity 59 defined by the membrane 54, the other of thewalls 57 and the other of the rigid outer surfaces 51. Also, the lens 50includes first and second pairs of channels 55 and 56 that extendthrough the walls 57 and respectively connect the first and secondcavities 58 and 59 with fluid reservoirs (see FIG. 5). In alternateembodiments, the channels 55, 56 can extend through the surfaces 51rather than through the walls 57. Also, while in FIG. 4 a there are apair of channels 55, 56 leading to each of the cavities 58, 59,respectively, in alternate embodiments there need be only one channel orthere could be more than two channels for one or both of the cavities(or, in some cases, only one of the two cavities might be accessible byone or more channels).

The lens 50 can be employed either as the convex lens 1 of FIG. 2 a orthe concave lens 2 of FIG. 2 b depending upon the pressures of the firstand second fluidic media 52, 53. When the pressure of the first fluidicmedium 52 is greater than that of the second fluidic medium 53, themembrane 54 bends towards the cavity 59 and the device behaves as aconcave lens for myopia. When the pressure difference between the twochambers is reversed, the lens behaves as a convex lens for hyperopia.The pressures within each of the fluidic cavities 58, 59 can becontrolled by one or more mechanical or electromechanical actuator(s)that determine the pressure and direction and rate of flow into or outof the cavities by way of the channels 55, 56. The curvature of themembrane 54 is determined by the pressure difference between thepressures within the cavities 58, 59 (as well as possiblycharacteristics of the membrane itself).

Regardless of the particular magnitude/sign of the pressure differencebetween the first and second fluidic media 52, 53 within the first andsecond cavities 58, 59, and regardless of the atmospheric pressure, theouter shape of the lens 50 does not change since it is defined by therigid outer surfaces 51. Thus, in contrast to the lens designs of FIGS.3 a-3 b, the lens 50 of FIG. 4 a does not require the maintaining of anegative pressure to achieve a concave structure, so the structure doesnot need to be made air-tight. Because the viscosity of air and liquiddiffers by many orders of magnitude, it is far easier to achieve aleak-tight structure than an air-tight structure. Finally, since it isthe fluidic pressure difference that determines the curvature of themembrane 54, that lens property is independent of the atmosphericpressure that is equally applied to both fluidic media 52, 53. On theother hand, temperature changes will cause a very minor index change ofthe media through the thermo-optic effect, having an unnoticeable effectupon the eyeglasses 5.

As for the lens 60 shown in FIG. 4 b, this lens employs two transparentrigid outer surfaces 61, two flexible membranes 62 positioned in betweenthe outer surfaces 61, and three walls 68 supporting the membranes 62 inrelation to the outer surfaces 61, where one of the walls is between thetwo membranes and the other walls are respectively positioned betweenthe two membranes and the two outer surfaces. The outer surfaces 61,membranes 62, and walls 68 define three cavities, one of which is aninner cavity 70 between the membranes, and the other two of which areouter cavities 69 on the other sides of the membranes. A low index fluid63 is provided into the outer cavities 69 defined by the walls 68, themembranes 62 and the two outer surfaces 61, and a high index fluid 64 isprovided into the inner cavity 70 defined by the walls 68 and the twomembranes 62. Three fluidic channels 65, 66 and 67 (or pairs or sets ofchannels) respectively connect the respective cavities 69 and 70 tofluid reservoirs (see FIG. 5), which can be two (e.g., one for the highindex fluid and one for the low index fluid) or three (e.g., onecorresponding to each of the cavities) in number.

When the pressure of the high index fluid 64 is greater than thepressure of the low index fluid 63, the lens 60 behaves as a convex lensfor hyperopia. However, when the pressure difference is reversed, thelens behaves as a concave lens for myopia. Because the lens 60 has rigidouter surfaces 61 as in the case of the lens 50, the lens 60 has thesame advantages as the lens 50 in terms of stability, reliability andperformance. In alternate embodiments, the high index fluid can be inthe outer cavities 69 and the low index fluid can be in the inner cavity70, or each of the cavities can contain fluid having the same index orhaving an index different than each of the other cavities.

Referring to FIG. 5, an exemplary hydraulic circuit 71 for controllingthe fluid pressure within a fluidic adaptive lens such as one of thelenses 36,46 of FIGS. 3 a and 3 b is shown. As shown, the hydrauliccircuit 71 includes a fluid reservoir 200 that is coupled by way of afirst valve 11 to one of the channels 39/49 of the lens 36/46.Additionally, the fluid reservoir 200 is also coupled, by way of aminipump 3 and a second valve 13, to another of the channels 39/49 ofthe lens 36/46. The minipump 3 (and possibly also the valves 11,13) iscontrolled by way of an electrical circuit 4. Also, a pressure sensor 9is coupled to a junction between the valve 11 and the lens 36/46,allowing for the pressure within the lens to be sensed. Based upon thecommands of the electrical circuit 4, the minipump 3 can operate to pumpfluid from the reservoir 200 into the lens 36/46 or, alternatively, pumpfluid from the lens back into the reservoir, assuming that the valve 13is in an open state. Depending upon the opening and closing of the valve11, fluid can also proceed from the lens back to the reservoir (orpossibly in the opposite direction as well).

The electrical circuit 4 controlling the hydraulic circuit 71 can takeany of a variety of forms including, for example, a microprocessor, aprogrammable logic device, a hard-wired circuit, a computerized deviceprogrammed with software, etc. The electrical circuit 4 can operatebased upon preprogrammed instructions or, alternatively, in response tocommands received from an outside source (e.g., in response topushbuttons pushed by a user, a received wireless signal, and othersignals). In the embodiment shown, the electrical circuit 4 can receivefeedback information from the pressure sensor 9 regarding the actualpressure within the lens 36/46, and base its operation upon thatfeedback information. Also, the mini-pump or actuator 3 can take on avariety of forms, or be replaced with a variety of other pumpingmechanisms. For example, the mini-pump or actuator 3 could be aperistaltic pump, a small frame-mounted pump, a piezoelectric actuator,a microelectromechanical system (MEMS) actuator, an electromagneticactuator, or a tunable integrated micropump such as that disclosed inU.S. provisional patent application No. 60/625,419 entitled “TunableFluidic Lenses With Integrated Micropumps” filed Nov. 5, 2004, which ishereby incorporated by reference herein. Also, pressure within the lens36/46 could be adjusted by way of a Teflon-coated set screw. The overallcircuit 71 might be battery-powered or powered in some other manner,e.g., by line power or solar power.

Although the hydraulic circuit 71 is shown in conjunction with one ofthe lenses 36,46, this type of hydraulic circuit, or several of suchcircuits, could also be employed in relation to the lenses 50,60 ofFIGS. 4 a and 4 b and other fluidic adaptive lenses. For example, two ofthe hydraulic circuits 71 could be used in relation to the lens 50 withits two cavities, while two or three of the hydraulic circuits could beused in relation to the lens 60 with its three cavities. The hydrauliccircuit 71 is intended only to be exemplary, and the present inventionis intended to encompass any of a variety of such circuits or othermechanisms that would be capable of adjusting the pressure of the fluidmedium within the lens 36/46. For example, depending upon theembodiment, two valves and channels linking the cavity of the lens 36/46to the reservoir 2 need not be used and, in some such embodiments, onlyone channel constituting an inlet and an outlet with respect to thelens, and/or one valve, might be necessary.

Turning to FIG. 6, a flowchart 73 shows steps of an exemplary procedurethat can be used to manufacture hydraulic circuits such as the hydrauliccircuit 71 of FIG. 5 that employ fluidic adaptive lenses such as thelenses 36,46 of FIGS. 3 a-3 b. Similar procedures could be used tomanufacture hydraulic circuits for controlling fluidic adaptive lensessuch as those in FIGS. 4 a-4 b. As shown, upon starting the process, ina first step 23, an open-ended cavity is formed using a plastic polymermaterial such as polydimethylsiloxane (PDMS) or polyester. The typicaldimension of the cavity would range from about one millimeter to a fewcentimeters in diameter and from about one tenth to a few millimeters inheight. The surfaces defining the cavity can be understood to includeboth the rigid outer surface 31/41 and the wall 37/47 shown in FIGS. 3a-3 b. Although primarily formed by the plastic polymer material, therigidity of the cavity surfaces (particularly the portion of itssurfaces corresponding to the outer surfaces 31/41) could besupplemented by bonding the plastic polymer material to a thin (e.g.,150 μm) glass slide.

In a second step 24, a thin plastic polymer membrane is formed, againpossibly through the use of PDMS. The membrane is flexible (albeit notpermeable), such that the membrane can be used as a flexible diaphragmseparating regions in which different fluidic media having differentindices of refraction are positioned. The membrane thickness typicallywould be on the order of about 30 to 100 μm. Each of the cavity and themembrane can be fabricated using a soft lithography process such as thatdiscussed in “Soft Lithography” by Y. Xia and G. M. Whitesides (Angew.Chem. Int. Ed. Engl. 37, 550-575 (1998)), which is hereby incorporatedby reference herein. Next, in a third step 25, the membrane formed instep 24 is bonded to the cavity formed in step 23 to form a closedcavity/chamber. The bonding could be achieved by way of an oxygen plasmasurface activation process, such as that discussed in “Three-dimensionalmicro-channel fabrication in polydimethylsiloxane (PDMS) elastomer” byB. H. Jo et al. (J. Microelectromech. Syst. 9, 76-81 (2000)), which ishereby incorporated by reference herein. When produced in large volumes,standard industrial processes such as injection molding and die castingcan be adopted to fabricate such lenses.

Then, in a fourth step 26, one or more channels 39/49 are formed alongthe wall/side of the lens 36/46 for the inlet and outlet of a fluidmedium into and out of the closed cavity. Although not necessary, thereare typically two channels per cavity, one of which constitutes an inletfor fluid when fluid pressure within the cavity is being increased andthe other of which constitutes an outlet for fluid when fluid pressureis being decreased. Although typically formed in the wall of the lens36/46, such channel(s) could alternatively be formed in the othersurfaces of the cavity, even in the membrane. Further, in fifth andsixth steps 27 and 28, respectively, the one or more channels areconnected to a fluid reservoir and to actuation components,respectively. As discussed above, the reservoir serves as a store offluid. The actuation components, which could include, for example, eachof the minipump 3, the valves 11,13 and the electrical circuit 4 shownin FIG. 5, cause fluid to be provided to the reservoir from the cavityand vice-versa. Finally, in a seventh step 29, a fluidic medium isintroduced into the cavity from the reservoir, and then the fabricationof the hydraulic circuit is complete, such that hydraulic circuitincluding the lens could then be mounted to/within the frame of a pairof eyeglasses such as those of FIG. 1.

Although FIG. 6 is directed toward the formation of a hydraulic circuitfor controlling a fluidic adaptive lens having one cavity such as thoseshown in FIGS. 3 a and 3 b and FIG. 5, the process could easily bemodified to allow for the creation of lenses such as those shown inFIGS. 4 a and 4 b and corresponding hydraulic circuits for controllingthe operation of such lenses. For example, the lens 50 could be formedby following the process of FIG. 6 and, additionally, forming a secondcavity at step 23 and attaching that second cavity in step 25 to theside of the membrane that was opposite to the side on which the firstcavity was attached. Additionally, the formation of a hydraulic circuitfor controlling the operation of the lens 50 would involve the formationof additional channels within the second cavity at step 26, theconnecting of additional reservoirs and actuation elements at steps 27and 28, and the introduction of a second fluidic medium at step 29.

Likewise, with respect to the lens shown in FIG. 4 b, in which there arethree cavities, one of which are between the two membranes 62, theprocess of FIG. 6 could be further modified to include additional stepswhere (1) a middle cavity is formed between two membranes (whichthemselves would typically be separated by a wall), (2) the twomembranes are then attached to the outer cavities, and (3) theappropriate formation of channels, connections to reservoirs andactuation components, and introduction of fluidic media areaccomplished. It should further be noted that, typically, when multiplecavities exist, at least two different fluidic media having differentrefractive indices will be introduced into the different cavities fromcorresponding different reservoirs. Any of a variety of fluidic mediacan be employed. For example, one of the media can be water (e.g.,deionized water) having an index of 1.3 and the other medium can be oilhaving a refractive index of about 1.6. Alternatively, other mediaincluding gaseous media such as air can be utilized. In alternateembodiments, the channels could also be formed prior to the combiningstep 25.

The use of fluidic adaptive lenses such as those discussed above withreference to FIGS. 2 a-4 b (and particularly those of FIGS. 4 a and 4 b)in eyeglasses provides numerous benefits. The fluidic adaptive lenses(and related hydraulic circuits) can be mass-produced as identicalunits, where the corrective power of each individual lens is set afterthe manufacturing process has been completed. Therefore the designoffers a fundamentally low cost solution from the production point ofview. Also, while optometrists can still determine the corrective powerof the fluidic adaptive lenses, the fluidic adaptive lenses also can bedynamically adjusted in terms of their corrective power by the eyeglasswearers themselves. This could significantly reduce the frequency withwhich eyeglass wearers might need to visit optometrists to obtain newprescriptions for eyeglasses. At a minimum, the time and costsassociated with obtaining eyeglasses with new prescriptions could besignificantly reduced since, upon visiting their optometrists for eyeexams, the optometrists could simply “tune” the wearers' existingglasses rather than order new glasses.

Further, even when eyeglasses are being replaced, patients will benefitfrom the use of tunable eyeglasses. Given the tunability of theirexisting eyeglasses, the patients will not need to suffer fromcompromised vision during the time period while they are awaiting theirnew eyeglasses. Additionally, because the fluidic adaptive lenses can bevaried continuously in their corrective power over a wide range, the useof these lenses makes it possible for optometrists to provide eyeglasswearers with lenses that more exactly suit the wearers' needs, insteadof merely selecting lenses that are the “nearest fit” to the wearers'needs from among a set of standardized lenses. Indeed, fluidic adaptivelenses could serve as a more graduated substitute for the solid-statelens set that optometrists use in determining their customers'prescriptions, and thereby allow optometrists to render more accurateprescriptions. Thus, fluidic adaptive lenses can be utilized inoptometrists' examination equipment. Additionally, fluidic adaptivelenses can eliminate any undesirable cosmetic effect for those who needbifocal lenses (or multi-focal lenses). Instead of utilizing bifocals, aperson can instead simply wear a single pair of eyeglasses that iscapable of being modified in its optical properties as necessary forperson's circumstance, e.g., based upon the flipping of a “dip switch”on the eyeglasses of the person.

To estimate the adjustment power of the fluidic adaptive lens 50 shownin FIG. 4 a, one can assume that the diameter of the lens is 20millimeters. Compared to the diameter change of a human pupil from about2 millimeters in sunlight to 8 millimeters in the dark, this lensdiameter is large enough for eyeglasses. Further, to estimate theadjustment power range of the fluidic adaptive lens 50, one can alsoassume that the low index medium is air with a refractive index of 1 andthe high index medium is water with a refractive index of 1.333. Using aray-tracing simulation program or the thin lens approximation for ananalytic solution, we have found that the maximum positive power andnegative power of the above fluidic adaptive lens is 12.8 D (diopters)and −12.8 D, respectively. Hence the total adjustment range for theadaptive corrective lens is from −12.8 D to 12.8 D, corresponding to anuncorrected visual acuity of 0.017 minute⁻¹ for hyperopia(farsightedness) and 0.022 minute-1 for myopia (nearsightedness).

Further, if silicone oil is utilized as the high index medium(refractive index is about 1.5) and water is used as the low indexmedium, then the total adjustment power range for such adaptive lensesbecomes from 6.4 D to −6.4 D, corresponding to an uncorrected visualacuity of 0.036 minute⁻¹ for hyperopia and 0.042 minute⁻¹ for myopia.Also, if silicone oil is used as the high index medium and air is usedas the low index medium, then the total adjustment range for the fluidicadaptive lens becomes from 19.2 D to −19.2 D, corresponding to anuncorrected visual acuity of 0.010 minute⁻¹ for hyperopia and 0.016minute⁻¹ for myopia. Although these estimates are for a fluidic adaptivelens such as the lens 50 of FIG. 4 a, corresponding estimates for othertypes of fluidic adaptive lenses (e.g., the lens 60 of FIG. 4 b havingthree cavities 63, 64) can also be readily determined. Also, a widevariety of fluids of different indices can be employed other thansilicone oil, water and air to make the lenses and allow the lenses totake on a variety of optical properties, which can be easily analyzedbased on the principles of geometric optics. Likewise, the particularmaterials used to form the rigid outer surfaces, walls and flexiblemembranes of the lenses can include any of a variety of plastic, acrylicand other materials, and can vary from embodiment to embodiment.

From experimental observations, several other performance aspects offluidic adaptive lenses have also been determined. In particular, it hasbeen determined that the fluidic adaptive lenses allow for dynamiccontrol over each of the focal length, power, field-of-view, F-number,and numerical aperture (NA) as a function of fluidic pressure within thelenses. Also, it has been determined that there exists no cleardependence of the image quality provided by fluidic adaptive lenses onthe thickness of their membranes. Resolution and image quality ingeneral suffers as the focal length increases beyond a certain length,where the pressure of the fluid is low (which, among other things, canresult in gravity having a non-negligible effect on the shape of themembrane). This problem can be corrected by using membranes of greaterstiffness, at the expense of higher power consumption and maximum powerrequirement on the mini-pump and actuator. Assuming the use of lensesthat are generally circular in shape, the membrane (except when flat dueto not being flexed) tends to have a generally spherical shape, albeitthe membrane tends to be somewhat flatter near its center. In at leastone experimental fluidic adaptive lens having a PDMS fluidic chambercovered by a 60 μm PDMS membrane and bonded to a thin, 150 μm glassslide, the relation between the focal length of the lens and the fluidicpressure within the lens was determined to be as follows: Ln(f)=−0.4859Ln(P)+7.9069.

Turning to FIG. 7, in accordance with certain embodiments of the presentinvention, two or more fluidic adaptive lenses can also be employed indevices that require multiple lenses. FIGS. 7-16 relate to variousimplementations of pairs of fluidic adaptive lenses to form zoom lenssystems (and, in particular, zoom lens systems that can be implementedin compact electronic or other devices). However, the present inventionis also intended to encompass other embodiments of multi-lens systemsemploying more than two lenses, lens systems in which one or more of thelenses are fluid adaptive lenses and other(s) of the lenses areconventional, solid (or other types of) lenses, and lens systems thatoperate to perform other functions besides or in addition to the zoomingfunctions that are performed by zoom lens systems.

Referring specifically to FIG. 7, a two-lens optical zoom system 78suitable for implementation in a compact electronic device such as acellular phone 79 is shown in a simplified schematic form. As shown, thezoom system 78 includes a front lens 72 (near an object) and a back lens74 (near an image of the object) that are separated by a distance(termed the “lens spacing”) d that is constant. In between the lenses,72 74, an optical medium 76 is typically situated. Depending upon theembodiment, the medium 76 between the two lenses 72, 74 can be any of avariety of optically transparent materials including, for example, air,glass, polymer, or anything transparent at the wavelengths of interest.For simplicity without losing generality, it can be assumed that both ofthe lenses 72, 74 are thin so that thin lens approximations can beapplied throughout the analysis. Each of the lenses 72, 74 has arespective imaging distance l₁ and l₂, respectively, the latter of whichis fixed. Zooming is achieved by varying the respective focal distancesf₁ and f₂ of the respective lenses 72, 74 (these and othernotations/variables used to describe characteristics of the two-lensoptical zoom system 78 are shown in FIG. 7).

Following the conventions of lens analysis, the variable Φ of a lens orlens system is defined as the power of the respective lens or lenssystem, which is also equal to the inverse (reciprocal) of the focaldistance f of the respective lens or lens system. Thus, while each ofthe lenses 72, 74 has its own values for Φ (e.g., Φ₁ and Φ₂,respectively), of particular interest for the two-lens optical zoomsystem 78 is an overall power of the system Φ_(τ). This quantity Φ_(τ)can be determined as a function of the respective powers Φ₁ and Φ₂ ofthe lenses 72, 74 and other parameters as follows:

$\begin{matrix}{\Phi_{2} = {\frac{1}{l_{2}} + \frac{1 + {\Phi_{1} \times l_{1}}}{{\Phi_{1} \times l_{1} \times d} + d - l_{1}^{\prime}}}} & (1) \\{\Phi_{\tau} = {{- \frac{d}{l_{2}}} \times \frac{\left( {\Phi_{1} + \frac{d - {2l_{1}}}{2d \times l_{1}}} \right)^{2} - \frac{d^{2} + {4l_{1} \times l_{2}}}{4d^{2} \times l_{1}^{2}}}{\Phi_{1} + \frac{d - l_{1}}{d \times l_{1}}}}} & (2)\end{matrix}$

Equation 1 shows that for given object and image plane distances (l₁ andl₂, respectively) and the lens spacing d, the power Φ₂ of the secondlens 74 (as well as the focal distance f₂ of that lens) is uniquelydetermined by the power Φ₁ of the first lens 72 (as well as the focaldistance f₁ of that lens). Further, Equations (1) and (2) together showthat, for a given object conjugate, the overall power of this two-lenssystem (Φ_(τ)) can be adjusted by varying the powers of both lenses Φ₁and Φ₂ (or, alternatively, the focal distances of both lenses f₁ andf₂). In comparison, conventional designs using lenses with fixed focaldistances (e.g., solid lenses) have to rely on varying the lens spacingd and the image plane distance l₂ to adjust the power of the system.Zoom ratio (ZR), a parameter of merit for zoom systems, is defined asthe ratio of the maximal achievable power and the minimal achievablepower (e.g., ZR=Φ_(max)/Φ_(min), both of which are values of Φ_(τ)).From Equations (1) and (2), it is evident that, to achieve a high zoomratio for given object and image plane distances, one should vary thefocal distances as much as possible. These concepts and conclusions alsohold for zoom systems having more than two lenses.

Although, in principle, the concept of zooming via varying the focaldistances could be applied using any type of fluidic adaptive lens, itappears that no tunable or adaptive lenses reported to date have had awide enough tuning range to be practical. For example, the shortestfocal length ever demonstrated in liquid crystal adaptive lenses isabout 200 mm for a lens aperture of around 5 mm corresponding to anf-number of about 40, which is insufficient to allow appreciable zoomingeffect. Both theoretical analysis and ray tracing simulation indicatethat highly effective zoom systems can be achieved only if the focaldistances of the lenses can be tuned continuously from a distance muchgreater than the lens aperture to comparable to or shorter than theaperture. In other words, for a 5 mm lens aperture, one would need toacquire a range of focal length from several centimeters to 5 mm orless, a value 40 times less than the shortest focal length demonstratedin state-of-the-art liquid crystal adaptive lenses.

Further, an even higher zoom ratio can be obtained if not only the focaldistances of the lenses but also the “types” of the lenses can beadapted or converted between being positive lenses (having a positivefocal distance such as in the case of a convex lens) and negative lenses(having a negative focal distance such as in the case of a concave lens)and vice versa. Liquid crystal adaptive lenses are (at least at thepresent time) incapable of being changed in their type.

In accordance with an embodiment of the present invention, the two-lensoptical zoom system 78 (or similar systems) when equipped with fluidadaptive lenses can achieve sufficiently high zoom ratios, withoutvarying the lens spacing d separating the lenses 72, 74 within thesystem. By using fluidic adaptive lenses, not only can the focaldistances of the lenses 72, 74 be widely varied or tuned, but also thelenses can be changed or converted in their type. FIGS. 8-17 concernvarious structures that can be used for the lenses 72, 74 and zoomsystem 78 as well as a fabrication technique for such lenses. However,the present invention is also intended to encompass other structures andfabrication techniques for creating zoom systems by way of fluidicadaptive lenses that will be evident to those of ordinary skill in theart.

FIG. 8 shows exemplary component structures of a fluidic adaptive lens75 that can be used as each of the lenses 72, 74 of FIG. 7. As shown,the lens 75 includes a deformable/flexible membrane (or diaphragm) 81that is coupled to the rim of a cup-shaped structure 85 having afluid-containing lens cavity 82 that includes a fluidic medium 83. Oneor more (in this case, two) channels 84 through the cup shaped structure85 allow for the fluidic medium 83 to enter/exit the cavity 82 from/to afluid reservoir (not shown). When the fluidic pressure inside the cavity82 changes, the curvature of the membrane 81, and therefore the lensshape, changes as well, producing different focal distances. Using anelastic silicone-based material (e.g., PDMS) of low Young's modulus(e.g., 1 M Pascals) as the membrane 81, a large lens shape change can beachieved and even a lens type change can be achieved (e.g., from aconcave or flat surface to a convex surface and vice-versa) as thepressure inside the lens chamber varies (e.g., from a negative to apositive value relative to the pressure outside the chamber). To achievean even broader tuning range of focal distance, one can use a high indexfluid as the lens medium. Over the spectral range of visible light,highly transparent fluid having a refractive index of 1.68 iscommercially available.

FIG. 9 shows exemplary dependence of the focal distance f of the lens 75on the fluidic pressure with different lens media, namely, deionizedwater (n=1.33) and sodium chromate (n=1.50), assuming a 20 mm lensaperture. As shown, not only can the focal distance of the lens 75 bevaried by modifying the fluidic pressure, but also the type of lens(e.g., concave/negative or convex/positive) as indicated by negative orpositive focal distance values can be changed by modifying the fluidicpressure. It is noteworthy that minimal focal distances (20 mm for H₂Oand 14 mm for sodium chromate in a positive lens and −17 mm for H₂O and−6 mm for sodium chromate in a negative lens) shorter than the lensaperture are demonstrated. As the previous analysis indicates, the useof one or more fluidic adaptive lenses having both wide focal distancetuning ranges and lens type convertibility makes it possible to achievea high performance zoom system without the need for varying the lensspacing between the lenses.

The flexibility in the choice of the materials from which the lenses 72and other components of the zoom system 78 can be built, andparticularly the flexibility in the choice of materials that can be usedto form the medium 76, offers many possibilities for forming “integratedzoom lenses” and for wafer scale production of lenses and lens arraysfor zoom systems. FIGS. 10 a-10 d show schematically how an exemplarytwo-lens structure 90 capable of being employed within the two-lensoptical zoom system 78 could be fabricated at low cost in an exemplarywafer-scaled batch process. As shown in FIG. 10 a, a transparentsubstrate (e.g., a glass substrate or polymer substrate) 91 of properthickness is chosen and two wafers 92 patterned with respective cavities96 are fabricated first. The patterns defining the cavities 96 can beformed using a soft lithography process (as discussed above withreference to FIG. 6) or a molding process. Then, as shown in FIG. 10 b,the two wafers 92 are bonded to opposing sides of the substrate 91 in amanner such that the cavities 96 are open outward away from thesubstrate. Although each of the wafers 92 is shown as including twocavities 96, the wafers could also have one cavity or more than twocavities depending upon the embodiment.

Further, as shown in FIG. 10 c, two handle wafers 94 each with arespective membrane 93 deposited along a side thereof are provided. Thehandle wafers 94 provide mechanical support for bonding the membranes 93onto rims 95 (as well as, in this embodiment, onto intermediate points,within the cavities 96) of the wafers 92. The bonding process caninvolve oxygen plasma surface activation (as discussed above withreference to FIG. 6) or other appropriate processes. Finally, as shownin FIG. 10 d, the handle wafers 94 are removed from the membranes 93,leaving the completed two-lens structure 90, which includes a firstfluidic adaptive lens body 97 capable of facing an object and a secondfluidic adaptive lens body 98 capable of facing an imaging plane. Wheremultiple such two-lens structures 90 are created simultaneously on asingle wafer (e.g., a single wafer comprising several of the substrates91) by way of a batch process, such two-lens structures can be separatedfrom one another by dicing the wafer into individual two-lensstructures. Once an individual two-lens structure 90 is obtained, it canbe employed in the two-lens optical zoom system 78 by connecting thetwo-lens structure 90 to a fluidic system (e.g., to fluidic reservoirsand actuating components such as those shown in FIG. 5), and filling thecavities 96 with the lens media of choice. Although channels allowingfor fluidic media inflow/outflow with respect to the cavities 96 are notshown in FIGS. 10 a-10 d, it is to be understood that such channels areprovided (e.g., as slots or indentations in the rims 95 of the wafers92).

Of significance during the process shown in FIGS. 10 a-10 d is thatthere be good alignment between the cavities 96 used to form the firstand second fluidic adaptive lens bodies 97, 98. Because all of thematerials of the two-lens structure 90 are transparent and the patternsare formed on large sized wafers, one can use either a contact aligneror the standard fixture of bonding machines (e.g., bonding machinesproduced by Karl Suss America, Inc. of Waterbury Center, Vt.) toroutinely achieve an alignment accuracy of a few micrometers. Assumingproper alignment of the cavities 96, the lens membranes 93 deposited onthe silicon handle wafers 94 can be bonded to the lens chambers withless alignment concern. The process discussed here allows fabrication ofzoom lenses of nearly any size (e.g., from <0.1 mm to centimeters) forvarious applications.

By way of this process shown in FIGS. 10 a-10 d, two-lens optical zoomsystems can be achieved on a high volume, low cost manufacturing basis.However, the present invention is also intended to encompass a varietyof other structures and fabrication processes than those shown in FIGS.10 a-10 d that can be used to create zoom systems that utilize one ormore fluidic adaptive lenses. Through the manufacture of such variousstructures by way of such various techniques, a variety of differentfluidic lens structures other than the structures 90 can be obtained inorder to meet different application requirements. For example, while thetwo-lens structure 90 of FIGS. 10 a-10 d would be adequate for someapplications, it would nevertheless be (as in the case of the lenses 36,46 of FIGS. 3 a-3 b) insufficiently robust for other applications due tothe exposure of the membranes 93 to the outside environment. Incontrast, FIGS. 11-16 show additional exemplary lens structures that canbe attractive for implementation in devices where, to improve therobustness of the zoom systems, it is desirable that the lens membranesnot be directly exposed to the outside environment or, even farther,desirable that all lens membranes be contained within the inside body ofthe zoom system.

FIGS. 11, 12 a and 12 b show additional fluidic adaptive lens structures100, 110 and 120 that can be employed as either of the lenses 72, 74 forconstructing two-lens optical zoom systems with better mechanicalrobustness than that afforded by the structure 90 of FIGS. 10 a-10 d.FIG. 11 in particular shows the lens structure 100 to include two outersurfaces 101 formed from a rigid material, a flexible membrane 102positioned in between the outer surfaces 101 and supported therebetweenby way of rigid walls 103. The outer surfaces 101, membrane 102 andwalls 103 surround and define first and second internal cavities 105 and106, respectively. The walls 103 also include fluidic channels 104 bywhich the first and second internal cavities 105, 106 formed between theouter surfaces 101 and the membrane 102 can be coupled to respectivefluidic reservoirs (or possibly the same reservoir) and actuationcomponents (not shown). The fluidic reservoirs provide first and secondfluidic media 107, 108, respectively, to the respective cavities 105,106. The first fluidic medium 107 typically (though not necessarily)differs in refractive index from the second fluidic medium 108, forexample, the first fluidic medium can have a lower refractive index thanthe second fluidic medium.

As for the lens structures 110 and 120 of FIGS. 12 a and 12 b, each ofthese lens structures includes a pair of flexible membranes 111positioned in between a pair of rigid outer surfaces 112 and supportedtherebetween by way of walls 113. In between the flexible membranes 111is defined an inner cavity 114, while in between each of the membranesand the corresponding neighboring one of the rigid outer surfaces 112 isdefined a respective outer cavity 115. The walls 113 contain inner andouter channels 116, 117 that respectively allow for fluidic media toenter/exit with respect to the inner cavity 114 and the outer cavities115, respectively. Typically, though not necessarily, the outer cavities115 receive the same fluidic medium while the inner cavity 114 receivesa fluidic medium different from that provided to the outer cavities 115.In the lens structure 110 of FIG. 12 a in particular, a first fluidicmedium 118 of lower refractive index is provided to the outer cavities115, while a second fluidic medium 119 of higher refractive index isprovided to the inner cavity 114. In the lens structure 120 of FIG. 12b, in contrast, the first fluidic medium 118 of lower refractive indexis provided to the inner cavity 114 while the second fluidic medium 119of higher refractive index is provided to the outer cavities 115.

The fluidic adaptive lens structures 100, 110 and 120 shown in FIGS. 11,12 a and 12 b each contain two media separated by one or two membranesdeformable by the pressure difference between the medium-containingcavities. For example, if the pressure in the higher refractive indexmedium cavity is greater than that in the lower refractive index mediumcavity, the membrane will bend towards the lower refractive index sideto form an effective convex lens. Conversely, if a higher fluidicpressure exists in the lower refractive index medium cavity, themembrane will bend towards the higher refractive index side to form aneffective concave lens. Thus, both the types of the fluidic adaptivelens structures (either negative or positive) as well as the focallengths of the fluidic adaptive lens structures can be modified/tunedvia dynamic control of the curvatures of the membranes of the lensstructures, which are determined by the fluidic pressure differencesbetween the two cavities on opposite sides of the membranes (andpossibly the characteristics of the membranes themselves). In the caseof the lens structures 110 and 120, the curvatures of the membranes areto some extent determined by the fluidic pressures in each of the threecavities rather than merely two of those cavities.

As discussed above, because the lens structures 100, 110 and 120 ofFIGS. 11, 12 a and 12 b have outer surfaces 101 and 112 that are rigid,the structures are more resilient to outside disturbances. It also makesthe fabrication process easier if these surfaces need to beanti-reflection coated to suppress undesirable light reflection.Further, because the outer surfaces 101, 112 are rigid, the externalshapes of the lens structures do not change even though the magnitudesand signs of the pressure differences between the cavities 105, 106, 114and 115 changes. Consequently, such lens structures 100, 110 and 120 canbe easily concatenated to form two-lens optical zoom systems such as thezoom system 78 as well as multiple-lens optical zoom systems (havingmore than two lenses) to achieve further increases in the zoom ratio.The pressure of each fluidic chamber/cavity can be controlled bymechanical, piezo-electric, electromagnetic, electromechanical, or otheractuators, such as those discussed above, and the curvature of eachmembrane is determined by the pressure difference between the twoadjacent chambers and the mechanical properties of the membrane(although, where a given lens has three chambers, the membranes'positions can be influenced by the pressures in all three chambers).While various liquids can be employed as the fluidic media 107, 108,118, 119, it should be understood from the above discussion that air (orsome other gas) can also be used as the low index medium. In the specialcase where air is used, a single-cavity fluidic adaptive lens can beconstructed by removing the cavities(s) for the lower refractive indexmedium.

FIGS. 13 a-13 b, 14 a-14 c and 15 a-15 d show exemplary two-lensstructures 122, 124, 126, 128, 130, 132, 134, 136 and 138 constructedwith various pairs of the fluidic adaptive lens structures 100, 110 and120 discussed with respect to FIGS. 11, 12 a and 12 b. As shown, each ofthe two-lens structures 122-138 includes a pair of the lens structures100, 110 or 120 that are separated by an intermediate optical medium 140that is positioned between the pair of lens structures. The opticalmedium 140 can take on a variety of forms, including forms such as thosediscussed above with respect to the substrate 91 of FIGS. 10 a-10 d, andthe medium can offer structural support for holding the pairs of lensstructures together as well as simply provide a transparent, opticallyconductive medium. More particularly, the two-lens structures 122-138combine the lens structures 100, 110 and 120 as follows. With respect tothe two-lens structure 122 of FIG. 13( a), this structure combines twoof the lens structures 100 having the same orientation, such that thesecond fluidic medium 108 of one of the lens structures is positionedcloser to the optically conductive medium 140 while the first fluidicmedium 107 of the other of the lens structures is positioned closer tothe optically conductive medium. As for the two-lens structure 124 ofFIG. 13( b), this structure combines two of the lens structures 100 inan oppositely-oriented manner, such that the same fluidic medium (in theexample shown, the first fluidic medium 107) of each of the lensstructures 100 is positioned closer to the optically conductive medium140.

With respect to the two-lens structures 126, 128 and 130 of FIGS. 14(a), 14(b) and 14(c), respectively, these structures respectively combinetwo of the lens structures 110 of FIG. 12( a), one of the lensstructures 110 of FIG. 12( a) along with one of the lens structures 120of FIG. 12( b), and two of the lens structures 120 of FIG. 12( b). Withrespect to the two-lens structures 132 and 134 of FIGS. 15( a) and15(b), respectively, these structures each combine the lens structure100 of FIG. 11 with one of the lens structures 110 of FIG. 12( a), whereFIG. 15( a) shows the lens structure 100 in one orientation and FIG. 15(b) shows the lens structure 100 in an orientation opposite to that ofFIG. 15( a). As for the two-lens structures 136 and 138 of FIGS. 15( c)and 15(d), respectively, these structures respectively combine the lensstructure 100 of FIG. 11 with one of the lens structures 120 of FIG. 12(b), where FIG. 15( c) shows the lens structure 100 in one orientationand FIG. 15( d) shows the lens structure 100 in an orientation oppositeto that of FIG. 15( c). FIGS. 13 a-13 b, 14 a-14 c and 15 a-15 d areonly intended to show some exemplary arrangements of the fluidicadaptive lens structures 100, 110, 120 to form exemplary two-lensstructures that can be implemented in two-lens optical zoom systems suchas the system 78 discussed above, and other arrangements of these andother fluidic adaptive lens structures are intended to be encompassedwithin the present invention.

Turning to FIG. 16, performance characteristics of a functional fluidicadaptive lens optical zoom system designed and fabricated according tothe process discussed above with reference to FIGS. 10 a-10 d are shown.The system employs water as the high index medium, and has a 20 mmaperture and an image distance of 50 mm. As shown, at an image distanceof 50 mm, the ratio of the maximal to minimal magnification factor is4.6 and 4.2 for object distances of 250 mm and 1000 mm, respectively.This yields a zoom ratio of greater than 3.

More generally, to estimate the zoom ratio of the zoom system, one cancalculate zoom lenses with 3 mm and 1 mm apertures assuming water(n=1.333) as the high index medium and air as the low index medium. Fora 3 mm aperture zoom system with a lens spacing (d) of 8 mm and an imageplane distance of 5 mm, one obtains a zoom ratio of greater than 4:1.Such a zoom system has a maximal field of view (FoV) of around 45degrees. For a 1 mm aperture zoom system with a lens spacing of 8 mm andan image plane distance of 1.5 mm, one obtains a zoom ratio of greaterthan 5:1. The maximal field of view for such a zoom lens is about 17degrees. If desired, one can obtain a zoom ratio of greater than 10:1 atthe expense of the field of view, assuming a lens spacing of 8 mm and animage plane distance of 5 mm. Finally, since the tunable lenses possessa shape of a spherical surface of a tunable radius of curvature, itproduces about the same amount of aberration as solid-state sphericallenses. Such aberration can be corrected with one or more asphericalsurfaces, a practice widely used by the optical system design community.

Although the fabrication process shown with reference to FIGS. 10 a-10 dis not exactly applicable to the construction of the lens structures100, 110 and 120 shown in FIGS. 11, 12 a and 12 b or to the fabricationof the two-lens structures shown in FIGS. 13 a-13 b, 14 a-14 c, and 15a-15 d, a number of fabrication processes for such lens structures arepossible. For example, FIG. 17 provides a flow chart 140 showing oneexemplary process for constructing the lens structures 100 and one ofthe two-lens structures 122 making use of a pair of those lensstructures 100. Upon starting the process, in a first step 141, cavitiesare formed on two separate pieces of transparent substrate. The diameterof the cavities can vary from a few hundred micrometers to a fewcentimeters depending on the application, and the thickness (depth) ofthe cavities could be in the range of a few hundred micrometers to a fewmillimeters. In a second step 142, a thin polymer membrane is formed.The membrane thickness typically is in the range of tens of micrometersto 100 μm and the membrane behaves elastically under stress, such thatit can be used as a flexible diaphragm separating the cavities to befilled with media of different indices of refraction.

Next, in a third step 143, opposite sides of the polymer membrane formedin the second step are respectively bonded to the respective pieces ofsubstrate with the cavities formed in the first step to form two closedcavities, one on either side of the membrane. Then, in a fourth step144, one or more channels are formed in the side walls of each of thecavities to provide inlets/outlets for the fluidic media (in someembodiments, a given channel or hole can act as both an inlet and anoutlet, while in other embodiments, dedicated channels are providedspecifically as either inlets or outlets). Then, in a fifth step 145,the inlets and outlets are coupled to one or more fluid reservoirs(typically, in this case, first and second reservoirs for first andsecond fluidic media). Further, in a sixth step 146, one or moreactuation components are incorporated to control the flow of the fluidicmedia into and out of the cavities (e.g., by varying the pressures ofthe fluidic media). As discussed above, these actuation components cantake on any of a number of forms including, for example, fluidicmicropumps, piezoelectric actuators, micro-electro-mechanic-system(MEMS) actuators, teflon-coated set screws, or other forms of actuationcomponents, to control and set the pressure of each fluid chamber.

Next, in a seventh step 147, two fluidic media of different refractiveindices are provided into the respective cavities. For example, one ofthe media can be water having an index of 1.3 and the other medium canbe oil having a refractive index of about 1.6 (in alternate embodiments,the fluidic media can have the same refractive index). This completesthe construction of one of the lens structures 100. To form the two-lensstructure 122, steps 141-147 would be repeated a second time, shown asan eighth step 148, to generate a second of the lens structures 100.Once two of the lens structures 100 have been fabricated, the two lensstructures at a ninth step 149 can then be mounted to an optical mediumconstituting the optical medium 140 between the two structures as shownin, for example, FIGS. 13 a and 13 b. As noted above, the optical mediumcan be, for example, a solid transparent substrate of certain thickness(e.g. a glass wafer or a polymer substrate). Thus, the process offorming one of the two-lens structures 122, 124 of FIGS. 13 a and 13 bwould be complete.

Other processes for fabricating the lens structure 100 of FIG. 11 aswell as the lens structures 110 and 120 of FIGS. 12 a-12 b are alsopossible, as are other processes for fabricating the two-lens structures122-138 of FIGS. 13 a-13 b, 14 a-14 c and 15 a-15 d. Once constructed,the entire optical zoom systems using the two-lens structures can takethe form of cylindrical tubes of a few millimeters in diameter and aboutone centimeter long. Such devices can be conveniently attached to manyhandheld or pocket-sized devices. To the extent that a zoom system canbe made into a compact attachment capable of being retrofit tocommercial optical systems, many additional products such as eyeglassesor goggles with zooming functions are possible.

It is specifically intended that the present invention not be limited tothe embodiments and illustrations contained herein, but include modifiedforms of those embodiments including portions of the embodiments andcombinations of elements of different embodiments as come within thescope of the following claims.

1. A lens device comprising: a first partition that is flexible andoptically transparent; a second partition that is coupled to the firstpartition, wherein at least a portion of the second partition isoptically transparent, and wherein a first cavity is formed in betweenthe first partition and the second partition; a first fluidic mediumpositioned within the cavity, the fluidic medium also being opticallytransparent; and a first component capable of controlling a parameter ofthe fluidic medium, wherein when the parameter of the fluidic mediumchanges, the first partition flexes and an optical property of the lensis varied, wherein the first partition is a flexible membrane formedfrom at least one of a thin plastic polymer and a flexible, opticallytransparent material, wherein the first partition is formed frompolydimethylsiloxane, wherein the second partition is a rigid partitionformed from at least one of a plastic and a material that is at leastpartly optically transparent, wherein the second partition includes atleast one channel allowing for the first fluidic medium to at least oneof enter and exit the cavity, wherein the second partition includes afirst portion that extends substantially parallel to the first partitionwhen the first partition is in an unflexed position and also includes asecond portion that extends substantially perpendicularly to the firstportion, and wherein the cavity is substantially cylindrical, the secondportion forms a substantially cylindrical wall around the cavity, andthe first partition and the first portion of the second partitionrespectively form first and second cylinder end walls of the cavity. 2.The lens device of claim 1, wherein the lens device is capable of beingcontrolled by the component to achieve a range of focal distances.
 3. Aset of eyeglasses including the lens device of claim
 1. 4. A systemincluding the lens device of claim 1, wherein the system is at least oneof a camera, a microscope, a video monitor, a video recorder, an opticalrecording mechanism, a surveillance mechanism, an inspection mechanism,an agile imaging mechanism, a target tracking mechanism, a copy machine,a scanner, a zoom lens system, a cellular phone, a personal digitalassistant, a computer, a magnifying glass, and a vision correctiondevice.
 5. A lens device comprising: a first partition that is flexibleand optically transparent; a second partition that is coupled to thefirst partition, wherein at least a portion of the second partition isoptically transparent, and wherein a first cavity is formed in betweenthe first partition and the second partition; a third partition that iscoupled to at least one of the first partition, the second partition,and an intermediate structure that is coupled to at least one of thefirst partition and the second partition, wherein a second cavity isformed in between the third partition and the first partition, andwherein the first partition extends substantially in between the secondand third partitions; first and second fluidic media positioned withinthe first cavity and the second cavity, respectively, the first fluidicmedium also being optically transparent, wherein a first side of thefirst partition is adjacent to the first fluidic medium and a secondside of the first partition is adjacent to a second fluidic medium; afirst component capable of controlling a parameter of the first fluidicmedium, wherein when the parameter of the first fluidic medium changes,the first partition flexes and an optical property of the lens isvaried; and a second component capable of controlling a second parameterof the second fluidic medium, wherein each of the first and secondcomponents includes at least one actuator selected from the groupconsisting of a peristaltic pump, a small frame-mounted pump, apiezoelectric actuator, a microelectromechanical system (MEMS) actuator,an electromagnetic actuator, a tunable integrated micropump, and aTeflon-coated set screw.
 6. The lens device of claim 5, wherein thefirst partition is a flexible membrane formed from at least one of athin plastic polymer and a flexible, optically transparent material. 7.The lens device of claim 5, wherein the third partition is rigid, andthe second and third partitions substantially surround the firstpartition so that the first partition is shielded from an outsideenvironment.
 8. A lens device comprising: a first partition that isflexible and optically transparent; a second partition that is coupledto the first partition, wherein at least a portion of the secondpartition is optically transparent, and wherein a first cavity is formedin between the first partition and the second partition; a thirdpartition that is coupled to at least one of the first partition, thesecond partition, and an intermediate structure that is coupled to atleast one of the first partition and the second partition, wherein asecond cavity is formed in between the third partition and the firstpartition, and wherein the first partition extends substantially inbetween the second and third partitions; first and second fluidic mediapositioned within the first cavity and the second cavity, respectively,the first fluidic medium also being optically transparent, wherein afirst side of the first partition is adjacent to the first fluidicmedium and a second side of the first partition is adjacent to a secondfluidic medium; a fourth partition that is coupled to the thirdpartition, wherein a third cavity is formed in between the thirdpartition and the fourth partition, wherein the third partition extendssubstantially in between the first and fourth partitions, and wherein atleast one of the first fluidic medium, the second fluidic medium and athird fluidic medium is positioned within the third cavity; and a firstcomponent capable of controlling a parameter of the first fluidicmedium; wherein when the parameter of the first fluidic medium changes,the first partition flexes and an optical property of the lens isvaried.
 9. The lens device of claim 8, wherein the third partition iscoupled to the first partition by way of the intermediate structure thatis an intermediate wall, and wherein the third partition is a flexiblemembrane.
 10. The lens device of claim 9, wherein flexing of the firstand third partitions depends upon relative pressures of the fluidicmedia within the first, second and third cavities.
 11. The lens deviceof claim 9, wherein the lens device is capable of being operated as atleast one of a convex lens, a concave lens, a plano-convex lens, aplano-concave lens, a convex-concave lens, a biconvex lens, and abiconcave lens.
 12. The lens device of claim 11, wherein the lens deviceis capable of being operated as at least two of the convex lens, aconcave lens, a plano-convex lens, a plano-concave lens, aconvex-concave lens, a biconvex lens, and a biconcave lens.
 13. Amulti-lens apparatus comprising: a first fluidic adaptive lens; a secondfluidic adaptive lens; and an intermediate structure coupling the firstand second fluidic adaptive lenses, wherein the intermediate structureis at least partly optically transparent, and wherein at least oneparameter of each of the at least one fluidic medium is controllable byat least one of means for providing fluid flow and means for varyingfluid pressure.
 14. The multi-lens apparatus of claim 13, wherein eachof the first and second fluidic adaptive lenses includes at least oneflexible membrane and at least one rigid surface that together define atleast one cavity within which is at least one fluidic medium.
 15. Themulti-lens apparatus of claim 14, wherein each of the first and secondfluidic adaptive lenses includes either one or two flexible membranes.16. The multi-lens apparatus of claim 13, wherein by controlling the atleast one parameter, a flexure of at least one membrane occurs thataffects at least one of a lens focal distance and a lens type.
 17. Azoom lens system including the multi-lens apparatus of claim
 15. 18. Asystem including the zoom lens system of claim 17, wherein the system isat least one of a camera, a microscope, a video monitor, a videorecorder, an optical recording mechanism, a surveillance mechanism, aninspection mechanism, an agile imaging mechanism, a target trackingmechanism, a copy machine, a scanner, a zoom lens system, a cellularphone, a personal digital assistant, a computer, a magnifying glass, anda vision correction device.
 19. A method of fabricating a fluidicadaptive lens device, the method comprising: providing a first structurehaving a first cavity, wherein the first cavity is only partiallyenclosed by the first structure; attaching a first flexible layer andthe first structure to one another in a manner that substantiallyencloses the first cavity, wherein the first cavity is capable of beingfilled with a first fluid so that the first structure, first flexiblelayer, and first fluid interact to form the fluidic adaptive lensdevice; providing a second structure having a second cavity, wherein thesecond cavity is only partially enclosed by the second structure; andattaching the first flexible layer and the second structure to oneanother in a manner that substantially encloses the second cavity,wherein the second structure includes the second cavity and a thirdcavity.
 20. The method of claim 19, further comprising: creating atleast one channel within at least one of the first structure and thefirst flexible layer that allows for communication of the first fluidwith respect to the first cavity.
 21. The method of claim 20, furthercomprising: coupling at least one fluid reservoir and at least oneactuator to the at least one channel to allow for communication of thefirst fluid with respect to the first cavity; and communicating thefirst fluid into the first cavity.
 22. The method of claim 19, whereinat least one of the first structure and the first flexible layerincludes at least one channel, so that the attaching of the firstflexible layer and the first structure to one another encloses the firstcavity except for the at least one channel.
 23. The method of claim 19,further comprising: affixing the first structure to a first side of anintermediate substrate; and affixing a second lens device, to a secondside of the intermediate substrate, wherein the first and second lensdevices and the intermediate substrate can be operated together as azoom lens system.